Assessment of the effects of satellite-linked telemetry tags on southern right whales over two decades

Abstract

The study of animal movement is critical in biological and ecological sciences. However, such studies are often challenging due to the difficulty of continuously observing wild animals. This is especially true for large baleen whales which can travel across vast distances in the open ocean. The use of animal‐borne telemetry tags, which allow for real‐time data collection of geographical positions of an individual, has therefore significantly advanced our knowledge on baleen whale movement patterns and currently forms an essential component of cetacean research. However, as satellite tags are invasive, there is concern about their potential effects on an individual’s health and wellbeing, and possible implications at the population level. Southern right whales (n = 21) were instrumented with Telonics ST‐15 consolidated satellite tags in 2001 in coastal South Africa. Fourteen of these individuals (13 females and one male) were photo‐identified either at the time of tagging or subsequently. Given the long‐term photo‐identification‐based monitoring of this population, 13 of these individuals could be resighted up to 21 years post‐tagging. This study builds on previous assessments of tag effects by providing an extra decade of information on sighting history and calving rates of the tagged individuals. Results showed no decadal tag effects when tagged whales were compared with untagged individuals. Visual assessment showed full healing of the tag site, with only small divots present in the last 10 years. Given the impact of environmental variability on the maternal body condition and reproductive success of this population, this study suggests no increased vulnerability to such stressors due to tagging. With 21 years of post‐tagging data, this is the longest follow‐up study on southern right whales to date. Considering the overall concern of the effect of tagging on the health and wellbeing of individuals, studies like these are critically important to ensure quality data collection with the least possible impact on tagged individuals.